uploads: fix broken tests.

* Fix broken upload tests.
* Fix uploads to return an error if both a file and a source are given
  at the same time, or if neither are given. Also fix the error message
  in this case so that it doesn't include "base" at the start of the string.
* Fix uploads to percent-encode any Unicode characters in the source URL.
* Add a max filesize validation to media assets.

test/functional/posts_controller_test.rb

@@ -5,6 +5,14 @@ class PostsControllerTest < ActionDispatch::IntegrationTest
     assert_equal(expected, response.parsed_body.css("link[rel=canonical]").attribute("href").value)
   end
 
+  def create_post!(user: create(:user), rating: "q", tag_string: "tagme", **params)
+    upload = build(:upload, uploader: user)
+    asset = create(:upload_media_asset, upload: upload)
+    post_auth posts_path, user, params: { post: { upload_media_asset_id: asset.id, rating: rating, tag_string: tag_string, **params }}
+
+    Post.last
+  end
+
   context "The posts controller" do
     setup do
       @user = travel_to(1.month.ago) {create(:user)}
@@ -638,6 +646,32 @@ class PostsControllerTest < ActionDispatch::IntegrationTest
       end
     end
 
+    context "create action" do
+      should "autoban the post when it is tagged banned_artist" do
+        @post = create_post!(tag_string: "banned_artist")
+        assert_equal(true, @post.is_banned?)
+      end
+
+      should "autoban the post if it is tagged paid_reward" do
+        @post = create_post!(tag_string: "paid_reward")
+        assert_equal(true, @post.is_banned?)
+      end
+
+      should "not create a post when the uploader is upload-limited" do
+        @user = create(:user, upload_points: 0)
+
+        @user.upload_limit.upload_slots.times do
+          assert_difference("Post.count", 1) do
+            create_post!(user: @user)
+          end
+        end
+
+        assert_no_difference("Post.count") do
+          create_post!(user: @user)
+        end
+      end
+    end
+
     context "update action" do
       should "work" do
         put_auth post_path(@post), @user, params: {:post => {:tag_string => "bbb"}}